The invention relates to a method for producing a high-density saline cesium and rubidium solution, i.e. a solution of a density of 1.6 to 3.3 g/cm.sup.3, by hydro-thermal decomposition of cesium- and rubidium-containing minerals.
A method for the hydro-thermal decomposition of a pollucite-spodumene concentrate for obtaining cesium carbonate is known from the magazine "Tsvetnye Metally--The Soviet Journal of Non-Ferrous Metals", vol. II, No. 5, pp. 57 to 59 (1961). In the process, the calcined minerals are subjected to hydro-thermal decomposition in an aqueous Ca(OH).sub.2 solution at 220.degree. C. and 20 atm pressure over a period of 4 hours, wherein optimum decomposition conditions are achieved with 3 mol Ca(OH).sub.2 per mol SiO.sub.2. It was possible to obtain 88.3% of the cesium contained in the mineral and to produce a cesium salt of a purity of greater than 99% by recrystallization of the alumino-cesium alum. A method for the conversion of Cs.sub.2 CO.sub.3 into CsHCO.sub.2 is furthermore known from the Chemical Abstracts article 79/4949v (1973), wherein the carbonate is reacted with formic acid in water.